Instrument for reaming root canals and sequence of instruments comprising at least such an instrument

ABSTRACT

An instrument for reaming a root canal, in particular in the apical zone housing at its proximal part a handle for manual use or on the head of a dentist&#39;s contra-angle handpiece, the distal part of said blade being a pointed tip of known type. The invention is characterised in that the active cutting part of the blade has, from the pointed tip and continuously, two conical sections such that, besides the pointed tip, each conical section has a greater taper ratio than the least distal part adjacent thereto. The invention is useful for reaming root canals with sequences of instruments avoiding root weakening and filling material flow at the canal end.

[0001] The present invention relates to the field of endodontic instruments for reaming the tooth canals, and more particularly to a specific instrument for reaming the tooth canals. The invention also relates to a sequence of instruments comprising at least one specific instrument of this type.

[0002] Endodontic treatment first of all involves mechanically reaming the root canal, then filling it, which is the final desired objective. Filling is done by adding an external material, for example gutta-percha.

[0003] The gutta-percha is usually introduced into the canal, prepared for this purpose, in the form of heated cones, the result of which is to soften the gutta-percha and thus render it malleable, and these are condensed by mechanical action with the aid of rammers in order to bring about “vertical” condensation or “lateral” condensation relative to the longitudinal axis of the reamed root canal.

[0004] The gutta-percha can also be arranged in the canal using the devices which are described in U.S. Pat. No. 5,588,835 or WO 93/14714.

[0005] These techniques and their purpose are well known to the person skilled in the art and are widely used on a daily basis by practitioners.

[0006] In the operations for mechanical preparation of a root canal, the practitioner generally attempts as far as possible to preserve the anatomy of the root canal, in particular to avoid weakening of the root as a result of excessive removal of substance. The tendency is herefore toward minimum reaming of the canal. When this aim is observed, the result is a conical reparation of small diameter at the apical level.

[0007] A consequence of this is that it is sometimes difficult to obtain a good filling with the methods described above. This is because these methods generally require, on the one hand, a wide canal preparation and, on the other hand, provision, at the bottom of the canal, of a seat-like bore which avoids the risk of the gutta-percha leaving the canal as a result of creep. It is therefore necessary to find a balance between these two constraints so as not to exaggerate the preparation in the upper part of the canal, which has the consequence of weakening the latter.

[0008] The principal object of the present invention is to make available a specific instrument for preparation of the root canal at the apical level, by which the abovementioned problems can be solved.

[0009] Another object of the invention is to make available a sequence of endodontic. instruments for reaming the root canals, comprising at least one specific instrument according to the invention.

[0010] More precisely, the invention concerns an instrument for reaming the root canals, in particular in the apical zone, receiving at its proximal part a handle allowing it to be used by hand or on the head of a dentist's contra-angle handpiece, the distal part of said blade being a pointed tip of a type known per se, characterized in that the active cutting part of the blade has, starting from the pointed tip and in continuity, two conical sections such that, in addition to the pointed tip, each conical section has a greater conicity than the least distal part immediately adjacent to it.

[0011] The invention also relates to a sequence of endodontic instruments for progressive reaming of the root canals, characterized in that it comprises at least one instrument of the above type.

[0012] The invention will be better understood from the following description of an operating method using a sequence of instruments according to the invention, reference being made to the attached diagrams numbered 1 through 7 which illustrate the progressive reaming of a root canal in order to obtain the desired root canal profile with an apical seat.

[0013] By way of illustration, the following sequence of instruments is used for example:

[0014] instrument No. 1 has an apical diameter of 0.20 mm and its conicity is 6%,

[0015] instrument No. 2 has an apical diameter of 0.20 mm and its conicity is 4%,

[0016] instrument No. 3 has an apical diameter of 0.20 mm and its conicity is 2%,

[0017] instrument No. 4 is identical to No. 2,

[0018] instrument No. 5 has an apical diameter of 0.20 mm and its conicity is 6% along 4 mm of the active length, then 3% along the rest of the active length,

[0019] instrument No. 6 has an apical diameter of 0.20 mm and its conicity is 8% along 4 mm of the active length, then 3% along the rest of the active length,

[0020] instrument No. 7 has an apical diameter of 0.20 mm and its conicity is 10% along 4 mm of the active length, then 2% along the rest of the active length.

[0021] The protocol starts off using instrument No. 1, which gives the canal the profile designated (1) in FIG. 1.

[0022] The instrument is engaged in the canal to approximately 7 mm from the apex. It will be seen that this first action determines the maximum reaming diameter and, consequently, the minimum depth.

[0023] The protocol continues using instruments No. 2, No. 3 and No. 4, which progressively ream the canal.

[0024] Instrument No. 3 is the first to be engaged to the apical level. It is this instrument which provides for the preparation of the apical diameter which will subsequently be observed by the rest of the sequence.

[0025] Instruments No. 5, No. 6 and No. 7 are then engaged in sequence, each to the apical level. Substance is extracted progressively as shown by the hatched areas in FIGS. 3, 4 and 5, in order to arrive at the desired profile of the canal with apical seat (8).

[0026] Advantageous general characteristics will be summarized below.

[0027] Thus, within the same series of instruments, the conicity of the most distal part increases from one instrument to the next in their sequential order of use.

[0028] Advantageously, at least two instruments in a series of instruments have a conical part of the same conicity.

[0029] This is, for instance, the case with instruments No. 2 and No. 4 in the example above.

[0030] Advantageously, each conical section of each instrument has an identical conicity for all the instruments of the same sequence.

[0031] Alternatively, for a given conical part, at least one instrument has a conicity different than that of the other instruments of the sequence in their equivalent part. 

1. An instrument for reaming the root canals, in particular in the apical zone, receiving at its proximal part a handle allowing it to be used by hand or on the head of a dentist's contra-angle handpiece, the distal part of said blade being a pointed tip of a type known per se, characterized in that the active cutting part of the blade has, starting from the pointed tip and in continuity, two conical sections such that, in addition to the pointed tip, each conical section has a greater conicity than the least distal part immediately adjacent to it.
 2. The instrument as claimed in claim 1, characterized in that it has an apical diameter of 0.20 mm and its conicity is 6% along 4 mm of the active length, then 3% along the rest of the active length.
 3. The instrument as claimed in claim 1, characterized in that it has an apical diameter of 0.20 mm and its conicity is 8% along 4 mm of the active length, then 3% along the rest of the active length.
 4. The instrument as claimed in claim 1, characterized in that it has an apical diameter of 0.20 mm and its conicity is 10% along 4 mm of the active length, then 2% along the rest of the active length.
 5. A sequence of instruments for treating the root canals, characterized in that it comprises at least one instrument as claimed in any one of claims 1 through
 4. 6. The sequence of instruments for treating the root canals as claimed in claim 5, characterized in that, within the same series of instruments, the conicity of the most distal part increases from one instrument to the next in their sequential order of use.
 7. The sequence of instruments for treating the root canals as claimed in claim 5, characterized in that at least two instruments in a series of instruments have a conical part of the same conicity.
 8. The sequence of instruments for treating the root canals as claimed in claim 7, characterized in that each conical section of each instrument has an identical conicity for all the instruments of the same sequence.
 9. The sequence of instruments for treating the root canals as claimed in claim 5, characterized in that, for a given conical part, at least one instrument has a conicity different than that of the other instruments of the sequence in their equivalent part.
 10. The sequence of instruments as claimed in claim 5, characterized in that it comprises seven instruments whose characteristics are as. follows: instrument No. 1 has an apical diameter of 0.20 mm and its conicity is 6%, instrument No. 2 has an apical diameter of 0.20 mm and its conicity is 4%, instrument No. 3 has an apical diameter of 0.20 mm and its conicity is 2%, instrument No. 4 is identical to No. 2, instrument No. 5 has an apical diameter of 0.20 mm and its conicity is 6% along 4 mm of the active length, then 3% along the rest of the active length, instrument No. 6 has an apical diameter of 0.20 mm and its conicity is 8% along 4 mm of the active length, then 3% along the rest of the active length, instrument No. 7 has an apical diameter of 0.20 mm and its conicity is 10% along 4 mm of the active length, then 2% along the rest of the active length. 